There are numerous compositions known to the art which can be compressed or tableted, providing a tablet, block or similar article which may be placed in the tank of a toilet and dispense cleaning active over a period of time. Such tablets may consist of, or include various cleaning agents such as bleaches, surfactants, disinfectants, and mixtures thereof. Menke, et al., U.S. Pat. No. 4,820,449 describes a toilet bowl cleaning block comprising 10 to 30% of a mono-alkyl sulfate salt, 5 to 40% of an alkanolamide, and 15 to 60% of a water-soluble inorganic alkali salt. Holdt, et al., U.S. Pat. No. 4,683,072 discloses a two-component, extruded cleaner and disinfectant tablet, comprising an LAS, an inorganic alkali metal salt such as carbonate, a plasticizer, an ethanolamide and an acidic or peroxy disinfecting agent, in combination with an LAS, plasticizer, and ethanolamide. U.S. Pat. No. 4,362,639 to Eoga claims a composition having an oxidizing agent (which may be a monopersulfate salt) a bleach promoter, a perborate salt and ammonium ion source. The bleach promoter is an alkali metal or alkaline earth metal halide, and the ammonium source is preferably an ammonium chloride, sulfate, citrate, or phosphate. Walker, et al., U.S. Pat. No. 4,741,853 discloses a solid cleaning block containing at least 60% of an alkali metal monopersulfate and the remainder an alkaline earth metal salt of a C.sub.12 -C.sub.24 fatty acid. Hung, U.S. Pat. Nos. 4,536,368 and 4,536,367 both teach a method of delivering a sanitizing agent such as a perborate, percarbonate, peroxide and persulfate in conjunction with a triphenylmethane indicator dye. Barford, U.S. Pat. No. 4,460,490 describes a shaped block having a slow-dissolving cleaning composition and a secondary tablet incorporating a bleaching agent. Monoalkyl sulfate and monoalkyl amide and hydroxymethylcellulose based cleaning tablets are disclosed for various uses, in U.S. Pat. No. 4,722,802, to Hutchings.
One of the difficulties which toilet bowl cleaning tablets of the art has been establishing a uniform release of active over a commercially feasible term (for example up to three months) and further to ensure substantially all of the tablet components dissolve at the same rate and with substantially the same endpoint. With particular reference to prior art, toilet bowl tablets which have a color and/or fragrance to indicate that the tablet continues to possess cleaning efficacy, the color and/or fragrance generally become imperceptible before the tablet is fully dissolved, and a residue typically remains in the tank, after the consumer believes the table has been fully used up. Furthermore, floating residue from an undissolved cleaning tablet in the toilet tank can contaminant toilet tank trim parts such as the flapper, water valve and overflow tube.
Accordingly, it is an object of the present invention to provide a composite tablet having improved dissolution of the total tablet to avoid the appearance of residue.
It is another an object of the present invention to provide a composite tablet having a long useful life.
It is another object of the present invention to provide a composite tablet having consistent cleaning performance over its useful life.
It is another object of the present invention to provide a composition that controls manufacturing and chemical costs by minimizing cost of ingredients needed to provide consumer aesthetic and cleaning performance benefits.